Glutamatergic circuits in the song system of Zebra Finch brain determined by gene expression of Vglut2 and Glutamate receptors

Abstract

Glutamateric neuron Brain In situ hybridization SongbirdThe songbird brain has a system of interconnected nuclei that are specialized for singing and song learning. Electrophysiological findings indicate a role for the glutamatergic neurons in the song system. Vesicular glutamate transporter 2 (vGluT2) is considered to be a specific biomarker of glutamatergic neurons in birds. Neurons receiving glutamatergic afferents express mRNA of ionotropic glutamate receptor subunits. This study examined expression of vGluT2 and glutamate receptor subunit mRNAs in nuclei of the song pathways of male zebra finch brain by in situ hybridization. VGluT2 mRNA was revealed high density of expression in the song nuclei, namely HVC, lateral magnocellular nucleus of the anterior nidopallium, and robust nucleus of the arcopallium. Area X did not show expression of vGluT2 mRNA. Nuclei in the descending motor pathway (dorsomedial nucleus of the intercollicular complex and retroambigual nucleus) were expressed vGluT2 mRNA. Target nuclei of vGluT2 mRNA-expressing nuclei showed hybridization signals for mRNAs of ionotropic glutamate receptor subunits. At least one of five subunit mRNAs (GluA1, GluA4, GluK1, GluN1, GluN2A) was expressed in song nuclei. The present findings support the existence of glutamatergic circuits in the song system in songbirds.

Thalamostriatal and cerebellothalamic pathways in a songbird, the Bengalese finch

“…V. Raju, Shah, Wright, Hall, & Smith, 2006; Dinesh V Raju & Smith, 2005). Future studies could test whether this approach would work in songbirds (Karim, Pervin, & Atoji, 2015; Karim, Saito, & Atoji, 2014), as suggested previously (Gale & Perkel, 2010).…”

Thalamostriatal and cerebellothalamic pathways in a songbird, the Bengalese finch

“…Another approach, commonly used to identify thalamostriatal synapses in mammals, is to stain for glutamate receptors vGlut1 and vGlut2, since it is known that thalamostriatal axon terminals in mammals preferentially express vGlut2 (while corticostriatal terminals express vGlut1) (D. V. Raju, Shah, Wright, Hall, & Smith, 2006;Dinesh V Raju & Smith, 2005). Future studies could test whether this approach would work in songbirds, as suggested previously (Gale & Perkel, 2010), although we note that to our knowledge only one antibody is available for vGlut2 in birds, and current reports suggest it would not strongly label the basal ganglia (Karim, Pervin, & Atoji, 2015;Karim, Saito, & Atoji, 2014).…”